The present invention relates to a cyclone or hydrocyclone for separating small particles from fluids.
Cyclones and hydrocyclones for the separation of suspended particles in fluids are well known. Scientifically, gases and liquids are both considered to be fluids. In this specification, the term xe2x80x9chydrocyclonesxe2x80x9d shall apply to devices which separate based on liquid-density differences and the xe2x80x9ccyclonesxe2x80x9d shall apply to devices which are used to separate particles from a gas.
Gases do not always behave in the same manner as liquids. Gases increase in viscosity as the temperature rises whereas liquid viscosity decreases. An example is when ash and other particles mixed in combustion gases emitted by a furnace incinerator are compared to air and sawdust exhausted from a wood manufacturer.
Cyclones and hydrocyclones have become increasingly common in the industrial world through their relatively low cost to manufacture and their ability to separate various phases from one another in phase mixtures such as liquid-solid,liquid-liquid, gas-liquid and gas-solid.
FIGS. 1 and 2 schematically shows the geometry of a typical prior art cyclone and hydrocyclone. All cyclones or hydrocyclones comprise an offset inlet (1) which causes the fluid to enter the cyclone tangentially with a swirling flow, a conical body (2), a vortex finder (3) where fluid overflow escapes and a solids outlet (4) at the bottom of the cyclone. Of course, exact configurations will vary between different manufacturers. These differences are related to entrance geometry, body shape, angle of cone, vortex finder, and the means by which fluid is taken to or from the cyclone or hydrocyclone. Over the years there have been many designs of cyclones and hydrocyclones. The prime difference in the different designs are related to mechanical layout and their resulting performance.
Conventional cyclones and hydrocyclones are able to separate particles from fluids down to a particle size of about 1 to 2 microns. FIG. No. 3 graphically shows the performance of various sized prior art hydrocyclones. Generally, separation ability increases with the differential pressure and inversely with chamber size. However, there is a lower limit of particle size which may be separated with a conventional cyclonic separator.
The present invention includes both cyclones and hydrocyclones and for convenience, the term cyclone shall hereinafter refer to both.
The present invention was developed when it was noted that submicronic clay particles naturally possess a small negative electrical charge. Because it is accepted that opposite electrical charges are attracted to one another, it was postulated that these electrically charged particles could be separated more easily from its host fluid (liquid or gas) medium at micron and sub-micron levels by augmenting the centrifugal separation forces in a cyclone with exposure to an opposite electrical charge within the cyclone.
The present invention presents an advance over the prior art in that electrical coulomb forces, electrical currents, and/or magnetic forces are combined with centrifugal forces to give an improved separating ability over conventional cyclones. Three embodiments of the present invention were developed: one utilizing coulomb or electrostatic forces; a second utilizing direct current; and a third utilizing magnetic fields. In all three embodiments, means are provided to physically and/or sonically vibrate the cyclone wall and fluid.
The efficiency of the cyclone is improved with the addition of either a coulomb charge or a direct current applied to the cyclone apparatus. In the case of particles affected by magnetic force, the application of a magnetic field will improve the performance of the apparatus. When magnetic forces were used, the importance of mechanical vibrations is especially pronounced in assisting the particles in being discharged with the under-flow.
The particles may be precharged prior to entering the separation chamber of the cyclone. The higher the voltage of the precharger, without shorting the electrical system out, the better the separation. Introducing electromagnetic fields with varied frequencies and amplitude strengths with vibrations also improved separation results.